PCM Excalibur 330 (5.7) — Stalls Under Load + MEFI Adapter Question

[paolozambelli]

Engine: PCM Excalibur 330 (5.7 L)
Year: Unknown, likely 2002–2007

Symptom​

• Revs freely to any RPM in neutral, forward, and reverse with no load.
• In gear under load (accelerating forward), it makes a fuel-starvation-type noise and dies.

Timeline / What happened​

• Boat sat ~3 months at a dealership for cosmetic work. After that, the fuel pump seemed stuck from sitting. I tapped the pump, and it worked fine.
• Later, the engine hit ~190 °F due to a clogged transmission oil cooler (R147014). I stopped, cleaned the cooler, and kept using it without issues that day.
• Then it sat ~1½ months. On the next outing, it started and idled great, but any hard acceleration in gear caused a stall. Light throttle at low RPM kept it running, but it felt like the fuel canister (with the filter) emptied. Cycling the key (ON, no crank) a few times refilled it enough to limp back to shore.

Work done so far​

• Fuel system: Replaced low-pressure and high-pressure pumps.
• Ignition: Replaced all 8 spark plugs (when removed, water came out of the plug holes). After changing plugs and manifold gasket there is no more water.
• Exhaust: Replaced exhaust manifold gasket (it was burned).
• Fuel pressure: Verified correct pressure at the service port.
• Distributor: Mechanic found the rotor/distributor (R103011) corroded (“sulfated”), as if moisture got inside the cap. Replacing this now.
• Next step: If needed, scan via MEFI.

What it feels like​

• Neutral: Clean revs anywhere, no stumble.
• Under load: Light throttle okay; hard throttle = stumble/die (sounds like fuel starvation).
• Fuel canister behavior: Seems to run dry under sustained throttle; key-on cycles refill it.

What I’m asking the community​

1. Likely culprits for stalling under loadeven after pump replacements and “OK” pressure at the service port:
   • Upstream restrictions/air leaks: anti-siphon valve, tank vent (test with cap loosened), pickup screen, FCC filter element, hose collapse, debris.
   • Ignition under load: moisture-affected cap/rotor, wires, coil, grounds (especially given the water/corrosion finding).
   • Water ingress: given water in the plug holes and a burned manifold gasket, anything else I should check (risers/elbows, gaskets, cracks)?
2. Year/ECM clues to narrow manuals/parts (any Excalibur 330 owners with similar vintage who can confirm ECM/MEFI variant?).
3. MEFI diagnostic plug help: My engine has a 10-pin MEFI diagnostic connector. My mechanic has a standard 16-pin OBD-II lead and wants to build a 10-pin adapter.
   • Does anyone have a verified pin-by-pin map from the 10-pin MEFI DLC to a 16-pin OBD-II connector that you’ve used successfully on this engine?
   • Which scan tool/software worked for you?

​

Thanks a lot!!​

 

[makomark]

Rev'ing in neutral is meaningless for 95% of the 'under load' issues...

What you've described doesn't explain the water in the cylinders item...I would be concerned about the condition of the exhaust elbows for a start.

"Fuel pressure ok" was determined (measured) under what conditions?

Does it have the 'crab' style distributor cap (HVS)? If so, be very leery on the aftermarket parts for that area...

on the 'adapter wiring' - I have pondered that one a few times but never found anything to go on so I'd set the bar low there. When you look at the time required to do it correctly, its highly likely to be more cost effective to buy a used techmate (or opt for the DIACOM s/w and cable) and be done with it. If you have the MEFI-4 controller (~ 2006 and earlier), you can read the codes with a paper clip, and LED and a resistor...

 

[paolozambelli]

Hi Makomark! thanks for your input, it is really valuable.

The exhaust elbows were checked when disassembling them to check the gaskets (one was burned and replaced) and the elbows were fine. Now there isn't any water coming into the cylinders as when I started it and left it on for a while I checked the spark plugs holes again and there was no humidity or water.

The fuel pressure was determined by accelerating forward or reverse in neutral and the odometer gave the right PSI pressure.

About the distributor, yes, it has the crab style cap (attaching pic)..so far my mechanic said he would clean it and replace it.

About doing the scan, i found this video on youtube, it seems that it is the way to do it with the paper clip.

I'll try that and see what codes i get.

Thanks again for your help!!

 

[makomark]

...
The fuel pressure was determined by accelerating forward or reverse in neutral and the odometer gave the right PSI pressure....

not sure what that means...to do it correctly, you need to have the boat in gear (under load) and monitor the fuel pressure across the RPM range...I usually do idle, 1500, 2500, 3000, and WOT. If the pressure isn't consistent, there's an issue with the fuel delivery system. The gauge pressure may change if the regulator is referenced to intake manifold vacuum.

given the corrosion in the distributor, it may not be a bad idea to change the relays in the harness...there are at least two, maybe three.

...

About doing the scan, i found this video on youtube, it seems that it is the way to do it with the paper clip.

...

Never seen that video - the 'continuity setting' may not work depending on the way the meter biases the test leads- if it doesn't reverse the leads. In any event, make sure you have the older MEFI 4 ECU - In 2007, they switched to a 'newer' model ECU. The MEFI-3 and -4 ECU's have the two harness connectors as shown in the video you posted.